Joining, connecting, and assembling hardened plastic parts



Mamh 1940- G. A: TINNERMAN 2,193,306

JOINING, CONNECTING, AND ASSEMBLING HARDENED PLASTIC PARTS Filed May 1, 1957 2 Sheets-Sheet '1 2/ Z3 2o -26 2 Z1 22 241 7 W M g5 i? .117. 7

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Mamh 1940.. G. A. TINNERMAN JOINING, CONNECTING, AND ASSEMBLING HARDENED PLASTIC PARTS Filed-May 1. 19s.? 2 Slagets-Sheet 2 Patented Man '12, 1940 UNITED STATES JOINING, CONNECTING, AND ASSEMBL'ING HARDENED PLASTIC PARTS George A. Tinnerman, Rocky River, Ohio, assignor, by mesne assignments, to Tinnerman Products, Inc., Cleveland, Ohio, a corporation of Ohio Application May 1, 1937, Serial No. 140,273 Claims. (01. -927 This invention relates to a method and means for joining in assembled relation hardened plastic and like parts, or for connecting a plastic part to tively yieldable elements easily and quickly applied in an aperture in a hardened plastic or like part to tensioned relation in rigid, anchored engagement in such part.

The manufacture and use of plastic molded objects in industry has, of recent years, assumed tremendous importance and is now produced by various methods under the trade names of Bakelite, Plaskon, Tenite, Catalin, Durite, Beetle, etc. Such molded objects have as the main ingredient some form of thermoplastic material such as resin, shellac, Celluloid, synthetic rubber, and the like. Suflicient of such material is mixed with a filler, coloring matter and lubricant and placed into a mold and subjected to heat and/or pressure, or both simultaneously. The plastic mix is thus transformed into a homogeneous solid mass which becomes hardened when subjected to a curing cycle.

The plastic parts which may be thus produced find a wide; and varied use in that almost .any object may be duplicated even to the, extent of the most difjllcult sizes and shapes. In addition, plastic parts are possessed of characteristics which make them more useful and advantageous in certain applications than the more common type of materials. Such characteristics, for example, are exceptional beauty, unusual dielectric properties, relatively high impact strength, high heat resistance, chip-, rust-, corrosion-, and shatter-proofness and extreme hardness, toughness and durability. 1

It is the property of extreme hardness which has heretofore made it difllcult and in some applications prohibitive to provide a satisfactory, inexpensive means -for securing separately molded parts of a plastic object in assembled relation or for connecting a plastic part to an associated cooperating part of different material. It is 0 to be understood that in themanufacture of ,cast of hollow, complementary parts which are suitably connected in assembled relation to pr0- vide the desired object or article; this procedure is followed not only because of the expense involved 1 in the use of large molds, but also from the standpoint of the increased weight and added material required in molding a relatively large object in one piece or in solid form.

Heretofore, in the fabrication of objects constructed of separately molded, cooperating or complementary parts made from plastic materials, the respective separately molded parts have been joined or connected in assembled relation either by the use of threaded metallic inserts molded into the plastic parts, the use of screw threaded fastening devices driven in tapped holes in the parts, or the application ofan adhesive-or cement to bind the parts. Due to the extreme hardness of plastic materials, the use of nails is impossible. Attempts also have been made to drive an apertured plastic part onto a rigid ratchet type shank but due to its extreme hardness, a plastic part is also relatively brittle, and will therefore crack and break under any concentrated blow or impact. It has been found that the use of threaded metallic inserts molded with the plastic parts'is objectionable and expensive in that they make for increased shipping weight of the object and require longer curing cycles for hardening; also, metallic inserts involve added costs in that they require the use of special forms and molding equipment to insure that the plastic composition will not disturb the position of the. metallic insert when being flowed into the mold. In the use of screw threaded fastening devices in plastic parts, a hole must be bored, tapped and the fastening device laboriously threaded into the tapped hole. This procedure is expensive in that it requires several time-consuming operations, results in weak threads that easily cross and tend to break quickly and which are, most often, not in proper alignment due to the infinite number of porous, rough spots, thin-walled gas pockets and other mold imperfections which prevent the screw threads of a fastening from being accurately and precisely threaded into a tapped hole in amolded article.

The use of an adhesive such as cement for uniting plastic parts has been found unsatisfactory in that it tends to dry out quickly and works loose dueto changes in atmospheric conditions and frequent handling. Then again, in employing a cement, the plastic parts must be subjected to an expensive and time-consuming fusing operation in order to obtain a satisfactory assembly.

It is therefore an object of thisinvention to provide a method of joining and connecting to which the fastening means may hardened. plastic and like parts in assembled rela tion in the use of fastening means which are most inexpensive, light in weight, durable, and ex-,

tremely simple to apply to anchored position in a plastic part.

It is a furthr object of the invention to provide a method of joining orconnecting a hardened plastic part to a cooperating part or object by anchoring a fastening means in such plastic part without the necessity of tapping a hole or providing a hole of specific configuration.

A still further object of the invention aims to provide a method of joining complementary plastic parts by fastening means having a plurality of shanks which are adapted toautomatically anchor into holes in the respective parts to hold the same in assembled relation.

Another object of the invention contemplates the provision of a method for assembling articles comprising hardened plastic parts by the use of securing means simplifying the assembly of such plastic parts without the necessity of adhesives,

cements or special assembling operations and equipment.

- A further object of the invention aims to provide a method of joining cooperating, complementary, hardened plastic parts in assembled relation joining or connecting in assembled relation a plastic part which is relatively thin and in which it is desired that the fastening means be con- I cealed from view.

A more specific object is for a method of joining or connecting in assembled relation a relatively thin plastic part by the use of a nub or boss will be apparent to those skilled in the art as a 4 description thereof .proceeds with reference to the accompanying drawings in which like reference characters designate like parts throughout the same and in which:

Figs. 1, 2 and 3 show generally the steps in the method of assembling complementary cooperating plastic parts in accordance with the invention, Fig. 1 illustrating a form of fastening means and the application of the respective shanks thereof to applied anchoring position in coopcrating hardened plastic or like parts;

Fig. 2 shows the final step in assembling the complementary or cooperating plastic parts represented in Fig. 1; a.

Fig. 3 is an end section view of Fig. 2 .taken along line 3-4; v v

Fig. 4 is a section view of Fig. 2 taken along line .4'4 illustrating the locking action of a shank memberof the fastening means in a substantially round hole in the plastic part;

Fig. 5 is a similar view as, applied to a substantially rectangular cavity in a plastic part;

Fig. 6 is a perspective view of the .fastener means 'per'se illustrated in Fig. 1, showing the locking leg elements of the shank members as offset. both in the same direction on the same side of the body portion of the fastening means; Fig. 7 is an end view of the device shown in Fig. 6;

Fig. 8. shows a modification in which a leg be. anchored I element of a shank member ofthe fastening means is provided with a cam shoulder permitting thesame to be withdrawn from the apertured plastic part to which it is applied; Fig. 9'shows in side elevation another form of 5 fastening means in which the locking leg elements of the shank members are offset in oppo- Fig. 12 shows in perspective a further form of 16 fastening means in which the locking legs are ofl'set in opposite directions on opposite sides of the body portion thereof;

Fig. 13 is a side view of the device represented in Fig. 12;

Fig. 14 is a side view of a still further form of fastening means in which the locking legs are oflset laterally in the same direction and on the opposite sides of the body member;

Fig. 15 is a perspective view of the'device represented in Fig. 14;

Fig. 16 shows a still further form of fastening means and in which thelocking legs are disposed directly opposite the body portion and are provided with prongs for engaging the side walls of the aperture in a plastic part;

Fig. 17 shows in end elevation the device of Fig. 16 as applied to an apertured plastic part;

Fig. 18 is a section view of Fig. 17 taken along as line II-I8;

Fig. 19 shows in perspective, a still further form of fastening means in which .the locking legs are corrugated such that their corner edges provide prongs adapted to anchor in a hole in a plastic part by digging into and becoming embedded in the side-walls thereof;

. Fig. 20 is a section of Fig. 19 taken along line Fig. 21 illustrates the method of joining'complementary plastic parts in a corner joint structure employing a form of fastening means of the invention;

Fig. 22 shows a method of assembling an obiect comprising complementary plastic parts, one

of which is relatively thin and in which the fastening means is hidden from view;

Fig. 23 shows a method of joining cooperating plastic and like parts one of which is relatively thin, the fastening means being exposed;

Fig. 24 isa section view of Fig. 23 taken along line 2l-24:

Fig. 25 shows a method of assembling an object comprising complementary hollow plastic parts employing a form of fastening means;

Fig. 26 shows a method of assembling a substantially cylindrical object comprising a piumolded members parts of which are shown broken away to show the function of the fastening means with a relatively thin member of the assembly,

and

' Fig. 29 is a section view of an end of the structure represented in Fig. 28.

nomical in that they may be constructed from 1 relatively light material such as sheet metal, cold rolled metal, wire and the like. In the drawings the fastening means are shown as constructed of sections of strip stock or blank stampings from relatively wide sheet material. Itis to be understood, however, that the particular form of fastening means shown are not the basic feature of the invention, since it will be obvious to those skilled in the art that other equivalent types of fastening means may be made in other forms and from all shapes of wire, orsimilar stock to function in the manner of the method herein taught.

It has been found that one of the cheapest, and at the same time most effective form of fastening means which may be employed in the method of this invention is obtained from a section of strip material or a suitable blank stamping, which section or stamping is bent back upon itself to provide a shank member comprising relatively yieldable leg elements at least one of which is provided with sharp, protruding, prong means, or the like, designed to anchor the shank member in theplastic part. As shown, the fastening means function best when the leg elements there- .of are integrally united to form" a leading end for the respective shank, which leading end is a in effect a substantial pilot element which readily seats in an aperture in a plastic part to which it is applied. ,However, it will quite readily be recognized that other forms of fastening means may be'embodied in the method herein taught wherein the shank memberscomprise relatively yieldable leg elements the leading ends of which are free and normally untensioned and designed to be brought together or otherwise compressed to permit insertion. thereof into an aperture in a plastic part in a press fit to thereby become tensioned to lock therein in applied-fastening I extremities of the free locking legs a position by reason of prong means, or the like, carried by at least one of the tensioned leg members anchoring into and becoming embedded within the aperture in the plastic part.

Referring to the drawings, Figs. 1, 2 and 3, reference characters A, B, represent a pair of complementary plastic parts, which together form a desired object'and in which it is desired that the fastening means be unexposed. Since the respective parts A, B are relatively thin and therefore could not inthemselves receive a shank C, D, are provided with suitable substantially aligned apertures or holes as shown in Figs. 4, 5, either in the molding operation of theplastic part, or by drilling the boss in any expedient manner in the finishing operation of, the plastic part in its hardened form. 1

Thus, in the assembling operation of the plastic parts A, B, Fig. 1, the nubs C, D are provided with. holes i, 2 which are in substantial alignment whereby a double-ended fastening means such as shown in Fig. 6 may be applied between the separated plastic parts with the respective leading ends of the shanks seated in the holes provided in the nubs. Upon pressure being exerted on the plastic parts to bring them together to assembled relation, the respective shank members of the fastening means advance in the:

holes .in which they are seated to become tensioned and thus anchored therein against reverse movement such that the plastic parts are held rigidly in the ,desired assembled .relation of the object asshown in Figs. 2 and 3.

In the form of fastening means shown employed in the assembly of Figs. 1-3 inclusive and as particularly illustrated in Figs. 6 and 7, the

device comprises a pair of fastening elements formed by bending the strip body It, back upon itself to provide shank members comprising relatively yieldable leg elements II, it and I2, integral in their leading ends to provide substantial pilot elements readily seated in holes in the nubs or bosses provided in the plastic parts. The free locking legs i3, M of the shank members may be offset laterally or in any other suitable manner such as to project the corners IE. it at theextremities thereof beyond the outline of their respective cooperating legs ii, i2 whereby such corners areeffective as prong means for anchoring the shanks in the bosses C, D,'

nubs, cam the side-walls of said holes to cause a gradual, lateral movement thereof from their normal, untensioned, laterally offset relation to tensioned relation in applied fastening position,

the diverging longitudinal edges presented by the offset legs facilitating such gradual, relative lateral tensioning movement of the leg members. When seated in applied fastening position in the assembled relation of the plastic parts, the prong elements l5, it provided by the camel;

, o the shank members; are caused to dig into and embed themselves in the adjacent side-walls of the-holes and thereby prevent looseness or reverse movement of the shank members from the respective assembled" plastic parts. Preferably, the holes in the plastic parts are of predetermined depth such that the leading ends of the respective shanks are seated against the bottom walls of such holes in order that the prong means of the free locking leg of each shank member may be designed to anchor in its hole in the plastic part at the most effective point depending on the relative thickness of thepart. This is most important in assemblies wherein one plastic part is of greater thickness than its complementary part such that it is most advantageous and often quite necessary to have one shank member of longer length than the other.

Although the fastening means is shown as comprising only two shank members, it is obvious that any desired number of integral shank mem- ,bers may be provided from a blank depending on the number of free ends which are provided and bent back to obtain the required shank legs. It is also obvious that a shank member may be molded directly into a plastic'part, boss or nub such that the remaining shanks are free to be applied to holes in cooperating plastic parts or II bosses carried thereby to maintain the complementary plastic parts of an object in assembled relation in accordance with the method. of the" ment M of the lower shank member is provided with a rounded shoulder H which engages under tension in the hole in plastic part B to satisfactorily hold the same in assembled relation, yet is capable of acting as a cam means permitting the shank member to be withdrawn.

Figs. 9 and 10 shows form of fastening means substantially similar in application and use to that disclosed in Figs. 6 and '7 but in which the holes in the respective assembled parts E, F, Fig. 11, need not be in substantial alignment. The fastening means of this form may comprise a body portion 28, the free ends of which are bent back on the same side thereof to provide the leg elements ii, 23 and 22, 2d of the respective shank members, the free legs 23, 24 being laterally offset to provide the locking prongs 25, it. Thus, in an assembly such as illustrated in Fig. 11 in which an object such as knob, panel or trim strip F having, if necessary, an apertured boss G, is mounted on a supporting apertured plastic part E, wherein the assembled parts need not be in exact position or adjustment with respect to each other, the holes in the respective parts need not be in exact alignment or precisely disposed. The fastening means of this form are balanced in engagement in the respective parts to be most effective in holding position clue to the fact that the locking legs 2 3, of the shank members anchor at diagonally opposite points in the respective parts in assembled relation.

Figs. l2'and 13 show afur ther form of fastening means embodying ofise't'locking legs. The device may beconstructed from a section of material comprising a body portion 3t, and the free ends of which are bent back on opposite sides of said body to provide shank members comprising relatively yieldable leg elements 3!, 83 and 32, 3d, the leg elements 33, 36 being ofiset laterally in opposite directions to provide locking prongs 35, 36.

Figs. 14 and 15 show a still further form of fastening means comprising shank members having relatively yieldable leg elements I, tit! and 42, 44, disposed on opposite sides of the body portion 40, the locking legs 43, 44 being ofiset in the same direction to provide the anchoring prongs 45, at.

Figs. 16-19 inclusive show another form of fastening means and its method of application to anchoring engagement in a plastic part. The device may be constructed from a strip the free ends of which are bent back to provide relatively yieldable, locking legs 53, 54 which are suitably notched to provide anchoring prongs on leg 53 and 56 on leg 54 respectively. Thus, when a shank member of this form offastening means is applied to a hole in the boss D" in a plastic part B", Fig. 17, the leg 54 will flex and yield as the shank is advanced to its home position whereupon the prongs 56 embed themselves in the hole to rigidly lock in the plastic part against loosening and reverse movement therefrom as exemplified in Fig. 18.

Figs. 19 and 20 show an alternate construction of this form of the fastening means wherein the free legs -63, 6d carried by main legs SI, 62 of the body portion 60, are corrugated transversely to protrude the corners 65, 56, which serve as anchoring prongs.

Figs, 21-29 inclusive illustrate various applications and uses of the fastening means in accordance with the method of the invention. In Fig. 21 a form of the fastening means designated generally as 3, is shown in applied holding position in holes I, 2 of complementary plastic parts H, I, in a corner joint structure, the fastening means being applied in substantially the method outlined with respect to Figs. l-3 inclusive. Fig. 22 represents a joint structure of complementary plastic parts J, K, one of which may be relatively thin to serve as a dial panel in a radio cabinet, for example. In such installations, it is desirable that the fastening means be unexposed and accordingly a boss J is provided on the relatively thin panel J, which boss is suitably'recessed to receive a shank member of the fastening means, the cooperating part K, being provided with a recess 2 to receive the opposite shank of the fastening means. Figs.'23 and'24 show a method for connecting a plastic part M to a relatively thin cooperating member L and in which it is not expedient to provide the same with a shank receiving fastening element. The plastic part M, is provided with holes 6, 2 in which are anchored the respective shanks i, 5 of a U-shaped fastening means including a body portion s, the fastening means being connected to the part L by means of apertures lit, to therein and through which the said shank members are passed. As shown in Fig. 2d, the shank members may comprise laterally ofifsetjrelatively yieldable leg elements applied to anchored engagement in the plastic part as outlined above. however that other forms of shank members, similar in use and comprising relatively yieldable leg elements'may be employed in accordance with the teachings of the herein described method. It is also obvious that only a single shank member need be employed, the portion 8 serving as the head member and to which a cooperating object may be connected by any suitable form of connecting means.

Figs. 25-29 inclusive show the instant method as followed in application to specific forms oi" hollow objects. In Fig. 25 an object in the form of a sphere or the like, is molded in separate parts N, 0' each of which .is provided with an integral boss or nub N, O, which are provided with suitable holes adapted to receive the shank It is obvious' members of the fastening means 3 as set forth with respect to Figs. 1-3 inclusive. Figs. 26 and 27 show a hollow, substantially cylindrical object comprising separately molded parts P, Q, R, held in assembled relation by a plurality of fastening means 8, the shank members of which engage in suitable holes provided at spaced points in i the respective parts, the holes preferably being blind, such that the fastening means are unexposed.

. Figs. 28 and 29 disclose an assembly of a spool- I plastic parts and having fastener receiving reprovided with suitable spaced holes which receive the locking shank members "I, of the fastening means such that the locking legs of the oppositely extending shank members 8 project connecting bosses thereon.

into the path of the mainbody portion T in assembled relation. Thus, when the member 'I' is advanced to assembled relation with the base parts S, U, the prongs presented by the locking legs of the shank members 8 are caused to become embedded in the adjacent inner side-walls of said member T and thereby resist reverse movement or loosening of the parts from as-. sembled relation.

From the foregoing it may be readily appreciated that the method herein disclosed solves a most difficult problem in the art of joining and connecting hardened plastic and like parts in assembled relation. It will also be observed that the problem is accomplished through the use of simple, inexpensive and easily and quickly applied fastening means of various types.

It will also be seen that the herein described method of assembling plastic parts is most advantageous in mass production since the type of fastening means employed in the method are effectively applied without theuse of the separate tools, involved, time-consuming assembling operations and special equipment.

While the method of the invention has been described in detail with specific examples such examples are illustrative only, since other modiflcations within the spirit and scope of the invention will be apparent to those skilled in the art. Hence the invention is to be understood as limited only as indicated in the appended claims in which the intent is to set forth all the novelty over the prior art.

What is claimed is:

1. In a fastening installation for light weight parts, a resilient connection for securing relatively thin hardened plastic parts in spaced re-' lation, said resilient connection comprising integral connecting bosses provided on said relatively thin plastic parts and having fastener re-' in the leading end thereof, said yieldable locking leg members being receivable in the recesses in the connecting bosses on said parts to engage therein under tension in applied fastening position with the anchoring prongs thereof embedded in the side-walls of said recesses, thereby resiliently holding said relatively thin plastic parts substantially locked in spaced assembled relation without causing fracture or breaking of said 2. In a fastening installation for light weight parts, a resilientconne'ction for securing relatively thin hardened plastic parts in spaced relation, said resilient connection comprising integral connecting bosses provided on said relatively thin cesses formed therein, and a securing device comprising a double-ended fastening provided from a strip ofmetal having its end portions bentto form yieldable locking legs, said yieldable locking legs being receivable in the recesses of said connecting bosses under tension in applied fastening position, thereby resiliently holding said relatively thin plastic parts substantially locked in spaced assembled relation without causing frac ture or breaking of said connecting bosses thereon.

3. In a fastening installation for light weight parts, a resilient connection for securing a relatively thin hardened plastic part to a cooperating part in spaced relation thereto, said resilient connection comprising an integral connecting boss provided on said relatively thin plastic part breaking of said connecting boss thereon.

4. In a fastening installation for light weight parts, a resilient connection for securing rela- V tively thin hardened plastic parts in spaced relation, said resilient connection comprising integral connecting bosses provided on said relatively thin plastic parts and having fastener receiving recesses formed therein, and a securing device comprising a double-ended fastener pro-' vided from a strip of metal having portions thereof bent to form yieldable locking legs provided with anchoring prongs, said locking legs being receivable in the recesses of said connecting bosses I'under tension in applied fastening position with the anchoring prongs thereof embedded in the side-walls of said recesses, thereby resiliently'holding said relatively thin plastic parts substantially locked in assembled relation without causing fracture or breaking of said connecting bosses thereon.

5. Ina fastening installation for light weight parts, a resilient connection for securing hardened plastic parts, said parts having fastener receiving recesses formed therein adapted to receive a substantial clip, said clip comprising a double-ended fastener provided from a strip of metal having portions thereof bent to provide distinct yieldable locking leg members provided with anchoring prongs, said yieldable locking leg members being receivable in said recesses in the hardened plastic parts to engage therein under tension in applied fastening position with the anchoring prongs thereof embedded in the sidewalls of said recesses, thereby resiliently'holding said hardened plastic parts substantially locked in assembled relation without causing fracture or breaking of said plastic parts in the area of said fastener receiving recesses therein.

GEORGE A. 'I'INNERMAN. 

